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Severe Allergic Reactions


Updated September 14, 2011


Anaphylaxis is a severe allergic reaction that can affect many organs of the body, including the skin, lungs, gastrointestinal tract, as well as the eyes, nose and throat.

Updated September 14, 2011

What is Anaphylaxis?

There is no single definition of anaphylaxis that is agreed upon by most experts in the field of allergy. In general, anaphylaxis is a life-threatening reaction caused by the release of chemicals, such as histamine, leukotrienes and tryptase, from mast cells. This may result in a variety of symptoms, including low blood pressure (shock), trouble breathing, and skin symptoms such as hives and swelling.

There are a number of causes of anaphylaxis, many of which are allergic in nature and involve allergic antibodies (IgE). However, not all causes involve IgE; exceptions include IV dye reactions and aspirin (NSAID) allergy.

What are the Symptoms of Anaphylaxis?

The symptoms of anaphylaxis vary, and may not all be present in a single person experiencing anaphylaxis. I tend to consider anaphylaxis when I see a patient with skin symptoms as well as the involvement of at least one other organ system.

Symptoms may include:

  • Skin symptoms, such as urticaria and angioedema, pruritus (itching) or flushing
  • Respiratory symptoms, such as shortness of breath, wheezing and coughing
  • Circulatory symptoms, such as rapid heart rate, lightheadedness and low blood pressure
  • Gastrointestinal symptoms, such as nausea, vomiting, diarrhea and abdominal cramps
  • Allergic rhinitis symptoms, such as sneezing, post-nasal drip and itchy nose and eyes
  • Other symptoms, such as menstrual cramps in women, metallic taste, sense of panic

What Causes Anaphylaxis?

There is a wide variety of causes of anaphylaxis, and therefore it is important for an allergist/immunologist to carefully review a person’s history in order to identify the cause of the reaction. Causes of anaphylaxis include, but are not limited to:

It is extremely rare for a person to experience anaphylaxis as a result of airborne allergens, such as pollens, molds, pet danders or dust mite allergen. However, these allergens commonly trigger hay fever and hives.

How is Anaphylaxis Diagnosed?

The diagnosis of anaphylaxis is usually made when a person’s symptoms are consistent with the syndrome. After a person’s history of symptoms, along with the events that occurred shortly before the onset of the reaction are considered, an allergist/immunologist can narrow the likely causes. Typically, skin testing can be performed for a variety of foods, medicines, venoms and latex in an attempt to identify the allergen. Various blood tests may also be performed to confirm anaphylaxis (such as checking a serum tryptase level), as well as other tests to ensure that a disease that mimics anaphylaxis is not the cause of the symptoms.

Next page: The Treatment of Anaphylaxis

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